Automatic train-control system



April 23, 1929.

w. K. HOWE 1,710,663

AUTOMATIC TRAIN CONTROL SYSTEM Filed May 24, 1919 2 Sheets-Sheet 1 FIG. 1 L 1 I [a T- I A w B 5 c 5 5 n {a Q ll Track.

' ATTORNEY April 23, 1929, w. K. HOWE AUTOMATIC TRAIN CONTROL SYSTEM Filed May 24, 1919 2 Sheets-Shet 2 Fl ca. 6 aw. i

Ill

BYW M A TTORNEY Patented Apr. 23, 1929.

-' UNITED STATES PATENT OFFICE.

WINTH ROP K. HQWE, OF ROCHESTER, NEW YORK, ASSIGNOR T GENEItAL RAILWAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

AUTOMATIC TRAIN-CONTROL SYSTEM.

Application filed May 24,

This invention relatesto automatic train control systems for railroads.

One feature of this invention is the provision for automatically exerting pressure upon the engineers brake valve handle at each caution signal, tending to move his brake valve to the service position, so that if the cngineeris incapacitated, or for any reason' fails to show that he is fully aware of the existence of danger ahead by taking hold of his brake valve handle and preventing its movement, an automatic service application of the brakes will be produced in the usual manner. This invention also contemplates the provision of automatic means for restoring the engineers brake valve to the lap po sition, after it has been operated to the service position automatically, as soon as the desired reduction in brake pipe pressure has been made, thereby obviating any objections which may be incident to the continued venting of the brake pipe.

Another feature of the invention resides in the efficient and reliable means for establishing. communication between the trackway and the moving car or train without physical contact between any parts on the track and the train. so that the operation of the system will not be influenced by snow, ice, or other adverse weather conditions.

Other specific objects and characteristics of the invention will appear hereinafter as the description progresses, and the novel teaturesof the invention will be pointed out in the appended claims.

my invention, I have illustrated in the accompanying drawings, in a simplified and diagrammatic manner, some of the various to terms oi construction which the several devices and combinations of devices embodying my invention may'talre; and these constructions have been shown more with the view of making it easy to understand and appreciate the characteristic features of a system embodying my invention than with the VlQW of illustrating the exact construction and arrangement oi parts which would be preferably used in practice.

In describing the invention in detail, reference will be made to the accompanying drawings, in which like reference characters For the purpose of disclosing the nature of 1919. Serial No. 299,488.

Figure 1 illustrates conventionally one arrangement .of trackway circuits suitable for use as a part of my system of automatic train control; i

Fig. 2 is a simplified and diagrammatic View, partly in section, which illustrates the construction of one form of brake controlling apparatus Fig. 3 illustrates diagrammatically one form of construction of the car-carried element and cooperating trackway element constltuting the means for transmitting controlilng impulses from the trackway to a passing rain;

Fig. 4 illustrates a modification of the carcarried element shown in Fig. 3;

Fig. 5 illustrates still another construction of the car-carried element and the trackway element;

Fig. 6 is a side view of the car-carried elemcnt shown in Fig. 5;

Fig. 7 illustrates astill further modified construction of the car-carried element;

Fig. 8 is a fragmentary View illustrating a modified formof construction of the movable armature constituting part of the carcarried element shown in Fig. 7;

Fig. 9 illustrates another modification of the tyne of car-carried element shown in Fig. 7 and Fig. 10 is a fragmentary view illustrating a still further modification of the construction shown in Fig. 7.

Considering first the trackway circuits shown in Fig. l, the track rails 1 of the railroad track are divided by insulated joints 2 into blocks in the usual manner. one block B with the adjacent ends of two other blocks A and 0 being shown. Since the parts and circuits associated with the various. blocks A, B and C are the same, thcv will be given, as

a matter of convenience, the same reference characters with distinctive exponents. Each of these blocks isprovided with a track battery 3 and a track relay 4. the same as in ordinary block signaling systems. Since my system of automatic train control is preferably used in connection with the usual fixed signals of the well known automatic block signaling systems, such signals S are indicated conventionally in Fig. 1; but since the various circuits and devices governing the indications and aspects ofthese fixed signals are well known to those skilled in the art, they have not been illustrated in order that the illustration might be simplified.

At an appropriate distance in the rear or the insulated joints 2 at the entrance to each block, (the normal direction of traliic being from left to right as indicated by the arrow), is located a trackway element T, which cooperates inductivelywith a car-carried element to transmit the desired controllinginfiuences or impulses to passing cars or trams. The controlling circuit for this trackway element T, (which in the form illlustrated in Fig. 1 includes a track battery 5) is controlled by a front contact of line relay 6. The controlling circuit for the line relay 6 includes front'contacts of the track relay of the corresponding block and also the track relay of the block next in advance, so that said line relay is energized when neither the corresponding block nor the next block in advance is occupied, and is deenergized when either of said blocks is occupied, all in a manner which will be readily apparent to those skilled in the art.

The trackway circuits shown in Fig. 1 are merely illustrative of a suitable arrangement by which the trackway elements of my auto matic train control system may be controlled in the proper manner so as to transmit a Cantionary impulse at each caution signal, or stop signal, and not to transmit such an impulse at a clear signal. Obviously, various modifications and alterations may be made in the particular trackway circuits illustrated Without departing from my invention, it being evident that various expedients may be. employed to obtain the desired opening and closing of the controlling circuit for the trackway element T in accordance with trafiic conditions.

The train control apparatus which I prcf- 'erably employ on the locomotive,-motor cars,

or other vehicles, is illustrated in a simplified form in Fig. 2, and comprises, generally stated, a pneumatic device which is set into operation at each caution'signal, by the deenergization of a controlling electro-pneuinatid valve to exert a yielding pressure tending to operate the engineers brake valve to the service position. The enginers brake valve being of well known construction is il-. lustrated in a conventional form and is designated E. The pneumatic device for. operating this brake valve may be attached to it in various ways, but in the construction illustrated, an arm 7 is fastened to the usual stem or shaft of the brake valve to which the engineers brake handle or lever 8 is applied. A sector gear 9, integral with or attached to the outer end of said arm 7, meshes with a rack 10, integral with or connected to, a rod 11, these various connections being prefer ably incased or constructed in such amanner that they cannot be readily taken apart maliciously by the engineer or other unauthorized person.

The rod 11 passes through one end of a cylinder D and loosely through a piston 12 in said cylinder, the right-hand end portion of the rod 11, as viewed in Fig. 2, being screwthreaded .and provided with adjustable clamping nuts 13, for the purpose hereinafter explained. Stops 1 1 are fixed to the inside of the cylinder D in position to limit the inward movement of the piston 12 toward the right, as viewed in Fig. 2. One end of the cylinder D, at the left-hand side of piston 12, as Viewed in Fig. 2, is in communication with the atmosphere through a device 15 of any suitable construction adapted to constitute an adjustable restricted orifice, and also with. a pressure supply pipe 16 leading to a control valve F. In the right-hand end of the cylinder D, is anotherpiston 17, which has its movement toward the left limited by the stops 14 and which is provided with an adjustable stop bolt 18 having a lock nut 19. The chamber in cylinder D at the right of piston 17 is in communication with the atmosphere, when said piston is at the left-hand extreme of its movement, through an adjustable re stricted orifice 20, and this chamber is connected to a supply pipe 21 leading to the control valve F.

The control valve F comprises a casing 22 anda differential piston 23. The larger end of the differential piston 23 is in communication through pipe 24 with the usual brake pipe of the well known air brake system; and the smaller end of said differential piston is in communication through pipe 25 with the main reservoir of the air brake system. The recesses and ports associated with the control valve F will not be specifically described,

since they will be explained hereinafter in connection with the description of the operation of the whole brake controlling device.

Whenever a caution signal is passed, an impulse is transmitted from the track tothe train, in the manner hereinafter explained, to cause decnergization of an electro-pneumatic valve, hereinafter referred to as the E. P. V., which acts to supply compressed air from the main reservoir through an adjustable restricted orifice 26 a small expansion reservoir 27, and pipes 28 and 29 to the control valve F. In addition to opening up communication in this manner, the electro-pneumatic valve 1*]. P. V. is also of the type which, after having once been deenergized and unseated. cannot be re closed upon energization of its controlling magnet until the pressure acting against the valve has been reduced to a predetermined amount. Various electro-pneumatic valves. capable of performing the desired functions. are well known in the art, and the type of valve illustrated, in Fig. 2 is merely illustrative of a construction suitable for use in my system of automatic train control.

As illustrated, this E. P. V. comprises a piston valve 30, which is normally held closed in the position shown by a stem 31 attached to the armature 32 of a controlling magnet 38, so as'to cut ofl communication from a chamber 34, to which pipe 28 is connected, through port 35 to chamber 36, to which pipe 29 is connected. When the magnet 33 is energized a valve 37 on its stem 31 opens communication from the enclosed chamber 36 to atmosphere through the exhaust port 38. Upon dcenergization of the magnet 33, the valve 30 and the stem 31 are forced downward by the pressure in chamber 34, this downward movement being also assisted by a compression spring 39 applied to the stem 31 in the usual manner.

The operation of the brake controlling apparatus just described need be only briefly explained. Normally the parts are in the position shown in Fig. 2. Upon deenergization of the magnet 33 at the caution signal, valve 30 opens and valve 37 closes, thus supplying main reservoir pressure from expansion reservoir 27 through pipe 28, chamber 34, port 35, chamber 36, pipe 29, cavity 40, port 41 in the differential piston 23, and pipe 16 to the cylinder Don the left hand side of piston 12. This pressure forces the piston 12 over against the adjusting nuts 13, and thus exerts a pressure upon the rod 11 tending to operate the engineers brake valve E to the service position. Unless the engineer, by holding his brake valve handle 8, preventssuch movement, the piston 12 is forced over against the stops 14, thereby op erating the brake valve E to the service position. The adjusting nuts 13, together with the stops 14, permit the engineers brake valve to be operated to the service position accurately. Vv'hen the engineers brake. valve E is operated to the service position, the brake pipe is vented in the usual manner to produce a service application of the brakes.

It will be noted that the area of the valve 30 exposed to pressure is greater when this valve is unseated than when itisclosed; and consequently, said valve 30 cannot be rcclosed by the magnet 33 until the pressure in chamber 34 has dropped to a predetermined amount. according to the size and proportion of the parts. If the engineer does hold 03 the automatic brake application, the pressure in the cylinder D gradually falls to the point where the valve 30 can be reclosed by the magnet 33, (this magnet being only momentarily deenergized, as explained hereinatter), by reason of the fact that the restricted orifice 15 is adjusted so as to be larger than the restricted orifice 26, so that air escapes to atmosphere through the orifice 15 from the'expansion reservoir 27 and connected pipes faster than it is supplied to said reservoir through the orifice 26. As soon as the valves 30 and 37 of the E. P. V. are restored to the normal position shown, the pressure in cylinder D and communicating pipes is exhausted through passage 38, and pressure from the main reservoir builds up in the expansion'reservoir 27,.ready for the next operation. It will be observed that this construction provides for applying pressure to the engineers brake valve E for a limited time, this time interval being adjustable to best suit the requirements of an installation by varying the size of the restricted orifices 15 and 26, as well as selecting thesize and proportion of the parts. This time interval is preferably much greater than that required to vent the train pipe, so as to assure a full brake application.

It is intended that the pressure produced by this brake controlling device upon the engineers brake valve E will be sutlicient to overcome the frictional resistance of said brake valve, but will not be so powerful that the engineer may not readily hold his brake valve handle against movement. It should be noted that this construction does not interfere with the ordinary operation of the brake valve by the engineer. The rod 11 passes loosely through the piston 12 and permits the engineer to operate his valve to the emergency position, as the occasion demands. Also, he may move his brake valve handle to the release position, if necessary, but inthis instance, he will have to overcome the pressure acting against the piston 12.

' The brake controlling apparatus so far de scribed merely serves to operate the engineers brake valve to the service position. For reasons well understood by those skilled in the art, it may be objectionable, however, to leave the brake valve in this service .posi tion for any great length of time; and I have also providedmeans for automatically rc storing the brakevalvc E to the lap position when the desired reduction in brake pipe pressure has been made. This is accomplished by the action of the differential pistori 23. When the pressure in the brake pipe has been decreased to the desired amount which corresponds to a predetermined fraction or ratio of a given )ressure in the main reservoir, the pressure rom the main rcservoir through pipe 25 acting against the smaller end of the diflerential piston 23 overbalances the brake pipe pressure acting against the large: end of said piston, and moves said piston to the right, as viewed in Fig. 2. This movement of piston 23 cuts otf pressure from port 41 and opens pipe 16 to atmosphere through cavity 42 and exhaust port 45% The pipe 21. which is normally in communication with the atmosphere through cavity 44 and exhaust port 45, is now placed in communication with the pressure in expansion reservoir 27 through cavity 40 and port 41. Thus, pressure is supplied to'the righthand side of piston 17, (which was moved to'the right by the movement of rod 11), and this forces the piston 17 to the left and causes the brake valve E to be restored automatieally to the lap position. When the piston 17 attains its extreme left-hand position, the restricted orifice 20 is opened, thereby gradually exhausting pressure from chamber 34 of the E. P. V., and permitting the piston valve 30 to reclose after a predetermined time. When the engineer recharges the brake pipe to release the brakes, the differential piston 23 is automatically returned to the normal position shown.

This arrangement has the further advantage that the engineer will not be required to hold his brake valve handle 8, if he makes an application of the brakes himself before passing the trackway element T at a caution signal. To illustrate, when the engineer reduces pressure in the train pipe to a predetermined amount, the ditlerential piston 23 will move to its right-hand position, so that when the E. P. V. opens, pressure is not applied to the piston 12 to operate the brake valve E to the service position. In this way,

if the engineer makes a full service brake application before the E. P. V. opens, he is not required to hold his brake valve handle 8. As previously explained, the E. P. V. does not close until after a short time; and if the engineer releases the brakes within this limited time after passing the caution signal, the differential piston 23 will return to its normal position and introduce pressure into the cylinder D against the piston 12. Thus, the engineer may avoid the trouble and annoyance of holding his brake valve handle 8 by making an actual application of the brakes before passing a caution signal, but he cannot release such brake application until after the lapse of the time for which the brake controlling apparatus is set. This timing may be varied as desired to best suit the special conditions in each instance by adjusting the restricted orifices 20 and 26.

The impulse transmitting means for controlling the magnet 33 of the E. P. V. may take various forms.

In the construction illustrated in Fig. 3, the trackway element T comprises a U-shaped permanent magnet with side projections 51 which afford a leakage path for flux of lower reluctance than that between the pole pieces 52 of said per manent magnet. Surrounding the legs of the permanent magnet 50, anddisposed above projections 51, are oppositely Wound coils 53 which are energized from the track battery 5 when the line relay 6 is energized. Thus, under clear trafiic conditions, when the line relay 6 is energized, current is supplied to the coils 53, which are so wound as to produce a magneto-motive force opposing that of the permanent magnet 50, thereby diverting this permanent flux through leakage paths, such as afforded by the projections 51.-

locomotive or passing vehicle, so as to pass directly over the pole pieces 52 of the track- .way element T. The air gap between the pole pieces of the car-carried element L and the trackway element T is preferably made as short as practical clearances on railroads will safely permit. This air gap, however, can readily be made large enough for all practical purposes by appropriately selecting the size and proportions of the various parts. The permanent magnets 50 are preferably located crosswise of the track, either outside or between the track rails, as best suited to the particular conditions, and the side members 54 preferably extend lengthwise of the vehicle for a distance suitable to obtain the desired duration of an impulse. A magnetic armature 55 is pivotally supported at one end to one of the side members 54; and this ar1na-' ture is biased by a spring 56, or equivalent means, away from the other side member 54, to the" position illustrated in Fig. 3. In this upper position of the armature 55, an insulated contact; finger 57 carried thereby cooperates with suitable fixed contacts, indi cated conventionally as arrows, and establishes a circuit for energizing magnet 33 of the E. P. V. i

The operation is as follows: lVhen the carcarried element L passes over the trackway element T under clear trailic conditions, the de-magnetizing coils 53 being energized, there is not sufficient flux through the side members 54 to overcome the bias of the armature 55, and the train may pass without operation of the i E. P. V. Under dangerous traffic conditions, however, the flux produced by the permanent magnet 50 passes through the side-members 5st of the. car-carried element L, and causes attraction of the armature 55 against the opposition of the spring 56, thereby opening the circuit for the magnet 33 of the E. P. V. and setting the brake controlling apparatus into operation.

In the modification shown in Fig. 4, the side members 54 of the car-carried element are connected by a magnetic core 58, having thereon a short-circuited coil or winding 59. The operation of this construction is substantially the same as that shown in Fig. 3, ex-

cept that the attraction of the armature 55 is dependent upon the speed of the train past the trackway element. This speed res onsive feature of this construction is due to t e core 58 and short-circuited coil 59. It will be evident that some of the flux transmitted from the trackway element to the side members 54 will pass through the core 58, and since this flux changes during the approach and passage of the train past the trackway element, a current is induced in the coil 59, this current being, in accordance with well known .laws, of a direction to oppose the passage of flux through the core 58. The amount of this current induced, and the extent of its bucking action will be dependent upon the rate of change of flux through the core 58, which in turn will depend upon the speed at which the train passes the trackway element. Thus, at high speeds, the passage of flux through the core 58 will be choked back so much that the greater proportion will pass th rongh the armature 55 and attract it to cause operation of the E. P. V.; butat low speeds, depending upon the size and proportion of the parts, so much of the total flux transmitted from the trackway element will pass through the core 58 that there will not be enough flux through the armature 55 to overcome its bias.

In the construction illustrated in Figs. 5 and 6, the trackway element T comprises two side members 60, angle-shaped in cross section, which are connected bya magnetic core 61 surrounded by a coil 62. These side members 60 preferably extend lengthwise of i the track for a sufiicient distance to influence the car-carried element fora short interval of time suitable for producing a strong and reliable operation. If desired, a number of cores 61 and coils 62 may be employed with the side members 60. The coil 62 is intended to be energized from a track battery under clear traftic conditions and to be deenergized under dangerous trailic conditions,as alreadyexplained,

- The car-carried clement L comprises two cores 63, which are provided with pole pieces (i l, and magnetizing coils 65. The cores 63 are supported in some suitable manner (not I shown), so as to pass over the side members 60 of the trackway element T Above the cores 63 is pivotally mounted an armature 66. As illustrated, this armature 66 is provided with trunnion pins 67 at one edge which 1 are held in adjustable bearings 68 carried by the energizing circuit of said coils, is a check relay 7 4 having a contact finger 75 and front contact included in the energizing circuit for the magnet 33 of the E. P. V. If the energizing circuit for the coils should become broken, or the battery depreciate, the contacts of the check relay 7 4 would open, thus operating the E, P. V. and calling attention tothe fact that the system was out of order.

The parts of the car apparatus are so proportioned and adjusted that, when the train is traveling between the signaling points, the flux produced by the energizing coils 65 is not sutlicient to attract the armature 66, this being due more particularlyto the large air gap between t-hepole pieces 64. Under clear traffic conditions, the coil 62 of the trackway element T is energized to give the side members 60 a polarity (as indicated), which opposes the polarity of the pole pieces 64. As

a result, there is not a suflicient increase in the flux produced by coil 65 to attract the armature 66. Under dangerous trafiic conditions, however, the trackway element T presents to the car-carried element a magnetic loop or brid e, so as to speak, which decreases the reliictance of the magnetic circuit through the coils 65 so much that, with the same current in said coils, sufficient flux is produced to attract the armature 66 and cause operation of the E. P. V. v

The modified construction of the carcarried element L shown in F ig. 7, comprises an inverted U-shaped yoke 7 6 of magnetic material having pole ieces 77 arranged to pass over the pole pieces of the cooperating trackway element. One leg of the yoke 76 is provided with two side extensions 7 8 and 79, constitutin in effect a shunt path or bypass tor flux through this leg of said *oke. Arranged between the ends ofthese sidis tensions 78 and 79 is a movable armature, which in the construction illustrated, comprises a bar 80 of magnetic material integral with or attached to a block which is yieldingly supported .from the extensions 78 and 79 by light springs 81. This manner of support not only provides a bias to the armature 80, but also supports it so that it is less sub jcct to movement by jar and vibration. The armature 80 carries an insulated contact finger 82 adapted to open the energizing circuit for the E. P. V. On the leg of the yoke 76 between the extensions 78 and 79 is a short-circuited coil 83. On the other leg of the yoke 76 is a coil 84=which is included in a normally closed circuit including a battery 85 and a check relay 86.

The check relay 86 is preferably of a balanced type which willcause operation of its circuit controlling elements when the current flowing in its coils is increased or decreased from a predetermined normal current for which the relay is adjusted. In theconstruction illustrated, the armature 87 of the relay 86 is biased by a spring, preferably adjustable,

and is provided with a striking piece of in-' .of one or the other contact springs 88 away from the fixed contacts 89. The strength of the battery 85, and the resistance of the coil 84 and the check relay 86, are so selected that, under normal conditions, the attraction ex-.

erted by the flow of current in the check relay 86 just balances its bias, thereby keeping the circuit for the E. P. V. closed. If thecurrent through the relay 86 decreased below its normal flow, due to a. breaking of the circuit,

or depreciation of the battery 85, the bias of the armature 87 .will overcome the tractive force of the windings of said relay, and thus open the E. P. V. circuit. Likewise, if the current is increased above the predetermined normal value, due to a cross or the like, the armature 87 will be attracted and will break the E. P. V. circuit. In short, the check relay 86 detects any failure of the circuit for energizing the coil 84, either by breaks or crosses.

Thecar-carried element L shown in Fig. 7, may be used in connection with any one of the various. types of *trackway elements illustrated; and when used with the trackway element T shown in- Fig. 5, for example, the operation is as follows: 'Under clear trafiic conditions, the coil or winding of the track way element is energized to present pole pieces of a polarity opposite to the polarity given to the pole pieces77 of the car-carried element L by the current flowing in the coil 84, so that there is little, if any, change in the flux through the yoke 7 6. Under dangerous trafiic conditions, the trackway ele ment presents in effect a dead magnetic loop which greatly reduces the reluctance of the magnetic circuit through the coil 84, so that with the same current flowing through this coil, a much greater flux passes through the yoke 7 6. This change in the flux through said yoke 76 induces a current in the short-circuited coil 83, which opposes the passage of flux through this leg of the yoke and causes some of it to be diverted through the extensions 78 and 79 and the armature 80, thereby exerting an attraction upon said armature 80 and moving it against the biasing force of the springs 81 to-open the circuit for the E. P. V.

In the modified construction illustrated in Fig. 8, an armature 90, of the Z-type, is employed instead of the single bar armature 80 shown in Fig. 7. The armature is supported by the springs 91 in substantially the same way as the armature 80, and carries an extension 92 adapted to separate the contacts included in the circuit for the E. P. V. This construction operates in substantially the same way as hereinbefore described in connection with Fig. 7'; but on account of the use of a Z-armatu're, the tractive force" upon the armature is exerted for a much greater range of movement, thereby pern1itting the parts to be arranged so that said armature may have a considerable idle movement before actuating its contacts. This aids in obviating any diflicult-y incident to the, vibration of the armature 90 by the jars and shocks to which it would naturally be subjected when carried on a train.

The construction illustrated in Fig. 9 is substantially the same as that shown in Fig. 7, the principal difference being that a permanent magnet 93 is employed in place of the yoke 76 and magnetizing coil 84, thereby dispensing with the coil 84, battery 85, and check relay 86. This construction operates in the same way as previously described.

In the construction illustrated in Fig. 10, an armature 94 of the shuttle type is mounted between the curved pole faces of the extensions 78 and. 79 and the windings 95 of this armature are connected. in closed circuit with the coil 83*. The armature 94 is provided with an arm'96, carrying a contact finger 97 for controlling the controlling circuit of the E. P. V. and a spring 98 is connected to said arm 96 and to a suitable fixed member so as to exert a biasing force tending to hold said arma-i ture in its normal position, shown in Fig. 10. The various parts, including the inductance of the coil 83 and the windings of the armature 94, are so selected that the 'current in the windings of said armature will, when the flux is sent through the yoke 7 6 as previously explained, be substantially in phase with that passing through the extensions 78 and 79 In this way, in addition to the torque exerted upon the armature 94 by virtue of the flux through said extensions 78 and 79 the current induced in coil 83 assists in actuating said armature by passing through the windings thereof and creating a field in cooperative relation with the field of flux between the pole faces of said extensions.

The various modifications in the construction of the car-carried element and the track way element, illustrated on the accompanying drawings, are merely typical and illustrative of the variousforms embodying my invention, and various other constructions and combinations involving the same principles and characteristics will be readily apparent to those skilled in the art. I desire it to be understood, therefore, that the constructions illustrated do not exhaust the various modifications which may be made in accordance with my invention. Those types of car-carried elements which include a magnetized yoke, or equivalent magnetic circuit, on the car, such as shown in Figs. 5 to 10, may be used .1

with a traclrway element of any one of the types shown in Fig. 3, or Fig. 5, the appropriate size and proportion of parts being, of course, selected for each combination for the best practical results. Furthermore, it is obvious that the various types of impulse transmitting means herein disclosed may be used with various forms oftrain control or brake governing appliances, and I desire to have it understood that my invention in this, as in many other respects, is not limited to the precise constructions and combinations of various devices illustrated and described.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In an automatic train control system, the combination with the air brake system of a railway vehicle, of automatic brake applying means operable to act upon the air-brake system and to cause an automatic application of the brakes, said brake applying means including a manually operable element by which the engineer may preventits operation, control means which if actuated operates said brake applying means, means partly on the vehicle and partly on the track cooperating inductively through an interveningair-gap for actuating said control means at predetermined control points along the track under unsafe traffic conditions ahead, and automatic means effective only if the brakes are manually applied to a predetermined degree by the engineer prior to the actuation of said brake applying means for preventing initial operation thereof even though said control means is actuated.

2. Inductive impulse communicating means for traincontrol systems comprising, a track clement providing spaced magnetic poles of opposite polarity in its active stopping condition, trafiic controlled means for rendering said track element ineflective a car-carried receiver comprising a partial magnetic circuit arranged to receive the magnetic flux emanating from said active track element, said partial magnetic circuit including two magnetically separated paths in multiple, flux responsive circuit controlling means magnetically associated with one path, and a winding on closed circuit magnetically associated with the other path.

3. A car-carried impulse receiving element adapted to respond to magnetic flux transmittedthereto from the tracliway, comprising means affording two partial magnetic circuits in multiple, and normally closed circuit controlling means jointly controlled by the rate of change and intensity of flux in said partial magnetic circuits.

t. In an automatic train control system, the combination with a track element constituting a magnet in the active stopping coning two flux paths in multiple, a biased armature magnetically included in one path, a winding magnetically associated with the other path, a brake control device, anormally energized circuit for maintaining said device inactive, and contacts in said circuit opened by a movement of said armature in opposition to its bias.

5. In an automatic train control system, the combination with the air-brake system of a railway vehicle; of an automatic brake setting device acting upon the ainbrake system to vent the brakepipe pressure to an amount representing a predetermined ratio of a preselected pressure; control means when actuatcd operating said brake setting device; automatic means for actuating said control means at predetermined control points along the track when dangerous traffic conditions exist; and means responsive to the dro in brake pipe pressure, and effective only i the engineer reduces said brake pipe pressure to at least the same ratio and prior to the actuation of said device, for preventing initial operation thereof even though said control means is actuated.

6. A train control system for railroads comprising, in combination with the air-brake system of a railway vehicle, of automatic brake applying means on the vehicle oper able to act upon the air-brake system and cause an automatic brake application; means effective only if the engineer manually applies the brakes to a predetermined degree prior to the operation of said means for preventing initial operation thereof irrespective of the speed of the vehicle; a traflic controlled trackway element; a receiver on the vehicle cooperating with saidtrackway element and having a partial magnetic circuit and a biased armature, said armature being magnetically moved in opposition to its bias by the trackway element in its active stop condition, and a normally energized circuit opened by said movement of said armature for controlling said brake applying device.

7. A car carried impulse receiving element for automatic train control systems comprising a core constituting a partial magnetic circuit with two multiple paths, a biased movable armature in one path, and a short-circuited coil associated with the other path.

8. A car carried impulse receiving element for automatic train control systems compris ing means constituting a'partial magnetic circuit with an air gap, a movable armature associated with said magnetic circuit, a winding magnetically associated with said armature, and means responsive to a change of flux in said magnetic circuit for energizing.

said winding.

9. A car carried impulse receiving element for automatic train control systems comprisi'ng a magnetic core, circuit controlling means magnetically associated with said core, and responsive to the rate of change of flux therei n, whereby the operation of said circuit controlling means is dependent upon the speed of the car.

10. In an automatic train control system, the combination with the air-brake system of a railway vehicle, of a brake setting device operable automatically to act upon the airbrake system and produce a brake application, means partly on the vehicle and partly on the track for imparting a control impulse to the vehicle at predetermined control points when danger traffic conditions exist, apparatus on the vehicle responding to said impulses and tending to operate said'brake setting device for a time and irrespective of the running speed of the vehicle, and means efiective only if the engineer manually applies the brakes to a predetermined degree prior to the operation of said brake applying device for preventing initial operation thereof and for continuing such prevention so long as the manual brake application is in effect irrespective of the speed of the vehicle.

11. A train control system comprising, in combination, the air brake system of a railway vehicle, a device operable to vent the brake pipe of said air-brake system, automatic means responding to the drop in brake pipe pressure for placing said device in condition to arrest further venting of the brake pipe after the pressure therein has been reduced to a predetermined extent, said means responding to the reduction in brake pipe pressure upon a manual application of the brakes and acting automatically to prevent initial operation of said brake applying device, only if and provided the reduction in brake pipe pressure by such manual application is tothe same or greater degree and occurs prior to the operation of said device.

12. In a train control system, the combination with inductive impulse communicating means including a track element constituting an inert body of iron when in its active stopping condition, said track element having a coil acting when in a closed circuit to render said element inactive, of brake control apparatus governed by said means and comprising, brake applying means tending tocau'se an automatic brake application, and means effective only if the brakes are manually applied by the engineer' to a predetermined degree prior to operation of said brake apply-- ing means for preventing the initial operation thereof.

13. In a train control system, the combination with a track magnet having opposite poles located alongthe track, of a car element having a partial magnetic circuit with an air gap, a biased armature spanning the air gap, means formin a flux path of high reluctance around sai armature when the car element passes over the track element, train control apparatus on the car, and circuit controlling means actuated by said armature for governing said apparatus.

14. In a train control system, the combina tion witha track element'constituting a magnet when in the stopping condition, of a car element for receiving flux from the trackelement, said car element comprising a biased armature and having aniron flux path in multiple with said armature, and a coil in closed circuit associated with said flux path and adapted to increase the reluctance of said path when the car element passes over the track element.

15. A car element adapted to respond to magnetic flux transmitted from the trackway and having two partial magnetic circuits in multiple, a biased armature in one of'said circuits, a coil in closed circuit included in the other of said circuits, and circuit'controlling means actuated by said armature.

16. In a train control system, the combination witha track element constituting a magnet when in the stopping condition, of a car element provided with two flux paths in multiple, a coil associated with one path and in which current is generated when the car elcment passes over the track element, and circuit controlling means associated with the other path and having its operation dependent on the flux in that path and also on the current generated in said coil.

17. In an automatic train control system, the combination with fluid pressure operated means for automatically applying the brakes by venting the brake p1pe,.control means for controlling the flow of fluid pressure to said fluid pressure operated means to efiect such venting under adverse trafiic conditions ahead, and means for controlling the flow of fluid pressure between said control means and said fluid pressure operated means to cause or arrest venting of the brake pipe depending upon whether the brake pipe has already been vented to a predetermined extent either manually or automatically. f

18. In an automatic train controlsystem. the combination with fluid pressure operated means for effecting an application of the brakes of the train by venting the brake pipc.;

control means for controlling. the flow of fluid pressure governing said fluid pressure operated means and effective to cause said fluid pressure operated means to vent the brake pipe under adverse traflic conditions ahead, and diiierential piston means having opposing pressures acting thereon one of which is a fixed pressure and the other of which is brake pipe pressure for controlling the flow of fluid pressure between said fluid pressure means and said control means.

19. In an automatic train control system. the combination with fluid pressure operated means for applying the brakes of the train by venting the brake pipe thereof, control means for controlling the flow of fluid pressure for controlling the fluid-pressure operated means to efiect such venting under adverse trafiic conditions ahead, and differential piston means for controlling the flow of fluid pressure between said control means and said fluid pressure operated means to determine venting of the brake pipe depend ing upon whether the brake pipe has already been vented to a predetermined extent either manually or automatically.

' WINTHROP K. HOWE. 

